Here's a Scala solution:
package controllers
import play.api._
import play.api.Play.current
import play.api.mvc._
object Application extends Controller {
  def index = Action {
    val app = Play.application
    var file = Play.application.getFile("pics/pic.jpg")
    val source = scala.io.Source.fromFile(file)(scala.io.Codec.ISO8859)
    val byteArray = source.map(_.toByte).toArray
    source.close()
    Binary(byteArray, None, "image/jpeg");
  }
}
Binary is a method of Controller, just like Ok. The source code in Results.scala suggests it will be deleted:
/** To be deleted... */
def Binary(data: Array[Byte], length: Option[Long] = None, contentType: String = "application/octet-stream") = {
  val e = Enumerator(data)
  SimpleResult[Array[Byte]](header = ResponseHeader(
    OK,
    Map(CONTENT_TYPE -> contentType) ++ length.map(length =>
      Map(CONTENT_LENGTH -> (length.toString))).getOrElse(Map.empty)),
    body = e)
}
But there is no suggestion of what to use instead. I suppose one could simply create one's own object to do this if required.